Rheostat



July 14, 1925. 1,545,843

L. w; MULVEY RHEOSTAT Filed April 23. 1924 i and useful Rheostat, of

Parental July 14, 192s.

UNITED STATES PATENT OFFICE.

LESTER W. I'ULVEY, 0F NEWBUBYPORT, MASSACHUSETTS, ASSIGNOR OF ONE-THIRDT0 @WARD E. CRAWSHAW, 0F NEWBURYPORT, MASSACHUSETTS.

RHEOSTAT.

Application led April 83, 1924. Serial No. 706,398.

To all wwm, t may cmwern. l

Be it known that I, Lns'rnn W. MULvEY, a citizen of the United States,residing at Newburyport, in the county of Essex and State ofMassachusetts, have invented a new which the following is aspecification.

The invention relates to improvements in rheostats, and to a means ofvarying gradually the electrical length, or resistance, of an electricalcircuit.

One form of the invention is illustrated in the accompanying drawing,which shows perspectively and embodiment of the invention. Thecylindrical conductor rod 10 is fitted to rotate axially upon pegs orstems 4 9 of relatively small diameter, protruding from the ends of theconductor cylinder, and extending into circular holes of slightliylarger diameter in two plane surfaced stan ards. The normally externalcontrol pe 4 is fitted with a knob 3 of convenient size or manualoperation. Suitable friction resistance to automatic rotation of theconductor cylinder is created by spring members 5 14 'pressed outwardlyfrom theends of the conductor cylinder 10 and against the standards11-12 which are paral el with each other andV each of which is in aplane at r1 ht angles with the axis of the conductor cy 'nder.Resistance wire in two conical coils 6 7, that ale fastened at the endof the conductor cylinder opposite to the knob or control end thereofand at the margin of the cylindrical surface close to the sectionthrough the cylinder consisting of the conductor cylinder, is attachedat the ends of the said wire to binding posts 1 13 set in the samestandard in which the knob or control end of the conductor cylinder isheld. The means of attachment of the wires 6 7 to the conductor cylinderat the point 8 fixes thereat the said wiresbut does not constitute anelectrical circuit between the ends of-*the said wires, which ends arenot in mutual contact. In operation the conductor cylinder 10 is rotateclockwise and reversely upon its axis by means of the knob 3, so that,by such rotation,the resistance wire 6 7 is caused to approach andgradually come into contact with the said conductor cylinder 10, firstat the end thereof opposite to the 'end to which the control knob isattached, when the said knob and conductor cylinder are rotated to theleft, that is to say, relatively to a point in front of the said knob,reversely to clockwise. When the said conductor cylinder is so rotatedthe length of the circuit from 1 to 13 is shortened gradually as thewire 6 7 becomes wound about the said conductor cylinder, which said rodmakes a circuit connection between the parallel coils of the saidspiral( wires. In operation, when the knob 3 is turned clockwise thesaid circuit is similarly lengthened and the electrical resistancethereof correspondingly increased. Thus in a given electrical circuit,constituted in part by the rheostat herein described, an adjustment ofthe resistance in such circuit may be made and maintained by means ofthe rotating of the control knob 3. It is obvious that the control knobmay, without departing from the spirit of the invention, be attached atthe end of the conductor cylinder at which end the said wires ,areaffixed. I particularly point out and claim as my invention: A

A rheostat comprising a conducting cylinder, standards for supportingsaid c linder for rotation about its axis, a plura ity' of spacedparallel resistance conductors helically disposed about said cylinderand having one set of adjacent ends connected together and attached tothe cylinder adjacent one end thereof, the free ends of said resistanceconductors bein pro"vided with stationary contact termina s, wherebyrotation of the cylinder more or less of the resistance conductors isbrought into electrical Contact with said cylinder to vary theelectrical resistance between the terminals.

I LESTER W. MULVEY. Witness:

EDWARD E. CRAWSHAW.

